A valve is a device that regulates the flow of a substance. Valves are produced in a variety of different styles, shapes and sizes. Typically, valves are used for gases and liquids. However, valves are also used on solids capable of flow, slurries or any other substance capable of flow. Valves are used in almost every industry having a substance that flows.
One type of valve is a gate valve, also referred to as a sluice valve. A gate valve opens by moving a blocking element from the path of flow. The blocking element may be a round disk, a rectangular element, or a wedge. Gate valves have a blocking element and a seat forming a substantially leak proof seal. In a gate valve, the blocking element can be referred to as a gate valve block, a gate block or a block. In the open position, a gate valve has a bore where the substance is allowed to partially or completely flow through the valve. In a gate valve, the bore may be referred to a gate valve bore. When the gate valve bore is across the valve bore the gate valve is in an open position. When the gate valve block is across the valve bore, the gate valve is in a closed position.
Gate valves may be operated manually or automatically. One method to automatically operate a gate valve is to use an actuator. An actuator is a mechanical device for moving or controlling a mechanism or system. When an actuator is used in a gate valve, the actuator is typically linked to a stem to repeatedly move the valve gate between open and closed positions.
Actuators to open and close the gate valves may include manual operators, diaphragm-type operators, pneumatic operators and hydraulic operators. Often, a manual operator is combined with a manual operator with a diaphragm-type, pneumatic or hydraulic operator for back-up and test purposes. Additionally, the actuator may include a bonnet assembly, which interconnects the valve body and the valve gate, and a bonnet stem which is movable with the gate via an operator.
A manual operator is often seen combined with diaphragm or hydraulic operator for back up purposes. These combinations generally result in a top shaft extending from the operator. The extension of the top shaft may indicate whether the valve is open or closed.
It is often desirable to be able to change the actuator without changing the bonnet assembly. This may prove difficult in implementation however, because changes in the actuator may require changes in upstop and downstop adjustments in order to ensure that the gate is positioned correctly when open and when closed. Additionally, drift shims have been traditionally employed to help adjust drift. However, the use of drift shims may require additional disassembly of the actuator for the installation.
While movement of the actuator housing against the bonnet may provide some advantages in correcting for valve drift, it may be desirable to have some actuator adjustment which is less prone to unwanted movement when the actuator is placed on a Christmas tree or other structure.
An additional adjustment device on a valve actuator located within the actuator housing or improved positioning and securement of a diaphragm may be desirable to overcome these obstacles.